No, for the real sound card DirectX (if you are on Windows) handles the sample rate conversion so everything should be right.
SDL which DOSBox uses for audio has far from alright sample rate conversion.

Anything but 49716 on both mixer and OPL, sounds distorted and noisy.
This applies to the Fast/Compat modes as well as for Nuked.

Awesome stuff! I'm currently listening to MegaRace's music right now and it sounds perfect! At first, the song "Maeva" was playing weird but it turns out I had the oplmode set to "opl3gold" (which I turned on earlier for my reverse engineer work on Dune and MegaRace's music format). Everything went back to normal once I switched the oplmode back to "opl3". Keep up the excellent work!

@nukeykt
Do you have a YM3812 version too of nukedOPL?
I ask because SB1.x,SB2.0,SBPro1 are still using the less accurate OPL2 emulation.

No. I cancelled it due to 2 reasons:
1) For me OPL2 sounds exactly like OPL3. Indeed, Nuked OPL3 sounds closer to OPL2 than any OPL2 emulator.
2) As i mentioned earlier, i'm busy with OPN2 emulator.
You can use OPL3 with blocked high ports. It will behave almost like real OPL2, except CSM(never was used), WSE bit(enables 4 waveforms on OPL2. These waves always active on OPL3)

A programmer friend asks a question about how nukedOPL enabled OPL2 modes:
"How do I set NukedOPL into OPL2 and Dual OPL2 modes?"

For OPL2 just ignore high bank writes. There are two ways to emulate Dual OPL2:
1) "True" Dual OPL2: Just run two instances of the Nuked OPL3 for each OPL2. But it would be heavy for CPU.
2) DOSBox way: Enable OPL3 mode. Set L/R panning. And just map first OPL2 chip commands to first bank, and second chip commands to second bank. You should also filter and block OPL3 specific commands. Look DOSBox source code for further information.

The friend in question is me. I am doing this in 86Box which is a fork of PCem. It uses (old?) dbopl.cpp, which has a variable that when turned off, makes the code pretend to be an OPL 2 and make the required adjustments. But nukedopl.cpp has no such switch and I'd rather not write my own code to do such adjustments because I have no idea how to do it right.

nukeykt,
Is this how dosbox does OPL2 with its cores, It just ignores high bank writes when using the opl core?
It seems that there is a separate OPL2 emulation in dbopl cores besides the OPL3.

DBOPL is a combined OPL2/OPL3 emulator. When OPL3 mode disabled it emulates OPL2, when you enable OPL3 it emulates OPL3. But in fact it only affects on WSE bit, which was removed in OPL3.
OPL3 in OPL2 mode should be good. OPL3 mode register is on high bank. So you never will be able to enable OPL3 mode with blocked bank. It'll stuck in OPL2 mode.

The friend in question is me. I am doing this in 86Box which is a fork of PCem. It uses (old?) dbopl.cpp, which has a variable that when turned off, makes the code pretend to be an OPL 2 and make the required adjustments. But nukedopl.cpp has no such switch and I'd rather not write my own code to do such adjustments because I have no idea how to do it right.

OPL3 was designed to be fully OPL2 compatibly. Yamaha added second register bank for extra channels. It's mapped to 0x222-0x223 and 0x38a-0x38b ports. Register which enables OPL3 mode is located on high bank. So it's enought to block writes to high bank.